Ian Rogers wrote a post showing how many of the albums reviewed in the June issue of Mojo (not that that's particularly eclectic) were available in Y! Music Unlimited. That post was 3 weeks ago, but here's the same test run on a single torrent site (differences are in bold):
Available
Robert Plant & The Strange Sensation - Mighty Rearranger
Blind Boys of Alabama - Atom Bomb
The Bravery - The Bravery
The Dissociatives - The Dissociatives
The Eels - Blinking Lights and Other Revelations
Fischerspooner - Odyssey
The Go-Betweens - Oceans Apart
New Order - Waiting For The Siren's Call
Garbage - Bleed Like Me
British Sea Power - Open Season
Saul Williams - Saul Williams
Kathleen Edwards - Back to Me
Konono No 1 - Congotronics
Alec Empire - Futurist
Natalie Imbruglia - Counting Down the Days
Martha Wainwright - Martha Wainwright
Tegan and Sara - So Jealous
The National - Alligator
Kaiser Chiefs - Employment
Jack Johnson - In Between Dreams
Loudon Wainwright III - Here Come The Choppers
Mark Mulcahy - In Pursuit of Your Happiness
Asian Dub Foundation - Tank
Petra Haden - Petra Haden Sings The Who Sell Out
Blak Twang - The Rotten Club
Daedelus - Exquisite Corpse
Autechre - Untilted
I Am Kloot - Gods and Monsters
Damon and Naomi - The Earth is Blue
Patrick Wolf - Wind in the Wires
Dead Meadow - Feathers
Alasdair Roberts - No Earthly Man
Unavailable at the moment (possible reason in brackets, mostly due to being released a while ago)
Ocean Colour Scene - A Hyperactive Workout for the Flying Squad (march 2005)
50 Foot Wave - Golden Ocean (march 2005)
Vic Chesnutt - Ghetto Bells (march 2005)
Adrian Belew - Side One (feb 2005)
The Features - Exhibit A (2004)
Burmese - Men (2004)
The Scott 4 Free Rock Orchestra - E-S-P
The Yards - The Yards
Van Der Graaf Generator - Present
Eliza Carthy - Rough Music (not released yet)
The Saints - Nothing is Straight in My House (march 2005)
Tom Russell - Hotwalker (march 2005)
Mose Fanfan - Bayekeleye
Taj Mahal Meets the Culture Musical Club of Zanzibar - Mkutano
Various - Chill: Brazil 3 (2004)
Fanfare Savale - Speed Brass of the Gypsies (2004)
Mary Lorson and Saint Low - Realistic
Terri Walker - L.O.V.E. (not released yet)
The Buff Medways - Medway Wheelers (march 2005)
The Witnesses - Tunnel Vision (2004)
Weird War - Illuminated by the Light
Nagisa Ni Te - Dream Sounds (march 2005)
Eric Matthews - Six Kinds of Passion Looking for an Exit (march 2005)
Angels of Light - ...Sing Other People (march 2005)
Big Business - Head for the Shallow (jan 2005)
The Bunnybrains - Box the Bunny
Avarus - Ruskea Timantti
...Bender - Bender
Thee Silver Mt. Zion Memorial Orchestra and Tra-La-La Band - Horses in the Sky (march 2005)
Kevin Mark Trail - Just Living (not released yet)
See also a comparison of Y! and Rhapsody for Pitchfork-reviewed albums.
Next someone has to do this with The Wire and see if any catalogue can provide above 10%.